In machine tools and other similar machines and apparatus it is often necessary to support relatively heavy structural components for precision movement along way surfaces.
The accuracy of machining depends on the accuracy of the motion of such components along their respective axis.
Simple plain bearings, used for many years, have more recently been replaced by various linear roller bearings in order to reduce friction. A successful version of such bearings is the so called recirculating roller bearing in which a series of roller elements move about a circulation path accurately ground into the periphery of a track member, with a surrounding and enclosing bearing cover confining the rollers in their recirculation path. The roller elements are exposed on one side of the bearing assembly such as to enable rolling movement along a way surface with the supported structure mounted to the bearing cover.
In order to achieve the accurate linear motion, the axis of the bearing assembly must be precisely aligned with the desired direction of motion of the supported structure, and this also prevents skewing forces tending to reduce bearing life.
In U.S. Pat. No. 4,544,211 entitled "RECIRCULATING BEARING ASSEMBLY" issued on Oct. 1, 1985, there is disclosed an improved recirculating roller bearing in which skewing forces are minimized in the bearing assembly.
Two sets of roller elements each circulate about the track member on either side of a central divider.
Installation of such bearing assembly in the supported structure typically involves precision machining of locating surfaces in order to properly align the bearing assembly within the supporting structure.
There is oftentime a need to provide adjustability of the bearing depth and in such instances a gib wedge plate package is provided in which a pair of plates having matching inclined surfaces are adjusted lengthwise relative each other in order to provide a adjustment of the depth of the installed bearing assembly.
Such bearing assemblies are typically installed in sets, each comprised of a number of variously facing bearings such as to engage a series of surfaces on the supporting structure, such as above and below a way surface and along a lateral edge. In such instances it is usual to provide such bearing adjustment for enabling precision adjustment of a supported structure and also for establishing a proper bearing preload by adjusting an opposing bearing assembly for reasons well known to those skilled in the art.
In such installations, considerable precision machining of the supported structure is necessitated which is difficult and expensive to accomplish on the usually relatively massive supported structures. Typically, as on a table, saddle, column, or similar structure, four sets of bearing assemblies are necessitated, one at each corner of the table.
Additionally, assembling the supported member carrying the bearing sets onto the supporting ways is a difficult operation.
Such recirculating bearing assemblies need to be lubricated in use and such installations necessitate additional machining and assembly labor to direct lubrication passages to each of the bearings in each set also adding to the manufacturing cost.
As noted, it has heretofore been known to provide an adjustment in such bearing assemblies by means of a pair of gib plates which are inclined and mate with each other disposed atop the bearing assembly such that lengthwise adjustment therebetween produces a height adjustment in the bearing assembly.
This arrangement typically includes a central slider or keyway with a key to maintain the perfect alignment of the bearing axis during the height adjustment.
It is also known to simply use a shim disposed above the bearing assembly in the housing. This likewise requires precision machining of the supported structure to fit the gib plate assembly into the supporting structure and the bearing assembly housing.
In order to simplify the assembly of the bearing housing onto the ways, separate bolted on sections are utilized, each having to be separately machined and precision aligned with the remaining structure.
U.S. Pat. No. 4,486,054 issued on Dec. 4, 1984 for a "RECIRCULATING ROLLING BEARING" disclosed an adjustable roller bearing assembly in which a cylindrical bearing housing is slidably fit into a bore slightly inclined to the bearing to enable a height adjustment. This requires a precision machined bore.